The invention relates to a double-tube radiator, composed of at least one double tube, preferably of aluminum, said tube being composed in turn of two tubes fitted concentrically one inside the other, said tubes having distributor stubs disposed at their end areas, each stub having a neck with a supply channel, running at right angles to the longitudinal axis of the tube, through which neck the oil or the like to be cooled is supplied to or removed from the double tube.
Such double-tube radiators are known. They are used, for example, to cool lubricating oil in engines or transmission oil in torque converters, automatic transmissions and the like in motor vehicles. In order to keep the heat-exchanging capacity at a high level, double tubes made of copper or aluminum are known to be used, wherein the oil is guided in the space between the tubes and therefore cooled from the inside and outside. In the known designs, the oil to be cooled is guided to the double tubes by distributor stubs disposed in the boundary areas of said double tubes. The double tubes are welded together in the vicinity of their ends. The distributor stubs are then soldered to the outer tubes. German Offenlegungsschrift No. 26 12 416 teaches such a double-tube radiator, wherein the distributor stubs are each composed of two parts. A tight connection between the distributor stub and the outer tube is created by screwing the neck of the distributor stub down so that a bead abuts the stub and provides a seal, with the seal improving directly as a function of the amount the neck is screwed into the stub. The disadvantage of the known designs is that the tubes must be cleaned internally after the two tube ends are welded or soldered; this is quite difficult. In addition, mechanical stresses are created by the difference between the thermal expansion coefficients of the water which is usually used for cooling and the oil to be cooled; this often causes leaks in the vicinity of the soldered joints. Still further, these known double-tube radiators can be disassembled only with difficulty, if at all, for cleaning.
Therefore, objects of the invention are to provide a double-tube radiator wherein the distributor stubs can be mounted on the double tubes without requiring soldering or welding, can easily be manufactured and/or repaired, and is immune to temperature-related leaks.
These objects are achieved in accordance with a preferred embodiment of the invention by equipping the distributor stubs with sealing plugs having cylindrical connecting areas, which can be mounted coaxially on the ends of the inner and outer tubes forming the double tube, each of said plugs being provided with a chamber communicating with a supply channel, said chamber being located between the connecting areas for the tubes. An important advantage of the present invention lies in the fact that the distributor stubs can be pushed over the ends of the tubes forming the double tube as plug-type connectors. The tubes thus come to rest against the corresponding cylindrical connecting areas provided on the distributor stubs. The endwise closure of the channel formed between the double tubes is also formed by the distributor stubs in the form of sealing plugs, so that the tubes need no longer be welded together endwise. Likewise, it is no longer necessary to solder the distributor stubs on the tubes or to fasten them otherwise, since the stub can be so adjusted in its connecting areas that an additional seat is ensured for the distributor stub on the tubes. The liquid to be cooled is fed through a supply channel to a chamber, likewise located in the distributor stub, said chamber being located between the connecting areas for the tubes and therefore feeding the liquid to be cooled, oil for example, into the channel between the tubes.
It is advantageous to design the chamber as part of a bore running coaxially to the axes of the tubes, said bore being provided on one side of the inlet of the supply channel with a connecting area for the inner tube, whose diameter corresponds to the outside diameter of the inner tube and merges with a connecting area for the outer tube on the other side of this inlet. Thus, the distributor stub has a bore whose diameter corresponds to the outside diameter of the inner tube on one side of the inlet of the supply channel, the inner tube being held in this area, and on the other side of the inlet, the bore has a diameter larger than the diameter in the connecting area of the inner tube, whereby the chamber can be formed in simple fashion. Since the connecting areas for the tubes are provided on the opposite ends of the coaxial bore, the outer tube is shorter than the inner tube inserted in the bore.
When the bore is provided, in a central area of the distributor stub, with a diameter which is less than the outside diameter of the outer tube and larger than the outside diameter of the inner tube, the chamber is produced in this area and runs coaxially to the longitudinal axes of the tubes. This permits the liquid to be cooled to be introduced over the entire circumferential area of the chamber, so that larger quantities of liquid to be cooled can be supplied without difficulty.
The connecting area for the outer tube consists, in a very advantageous fashion, of a cylindrical stub whose outside diameter corresponds to the inside diameter of the outer tube. In this embodiment, the inner tube is then received in the bore of the distributor stub and the outer tube is fastened at its outer circumference in the vicinity of the cylindrical stub. Since this causes the outer tube to extend over the cylindrical stub of the distributor stub, the heat-exchanger walls are enlarged without necessitating an increase in the size of the distributor stub. This results in a high degree of heat-exchanger efficiency. Moreover, this can also result in a relatively large throughput cross section between the two tubes, thus facilitating the introduction of larger quantities of fluid.
The manufacture of this cylindrical stub can be accomplished in simple fashion if the cylindrical connecting stub is part of a housing wall which surrounds the bore running coaxially to the axes of the tubes, said wall merging with the end away of the cylindrical stub in the connecting area for the inner tube.
It is advantageous for the connecting areas for the tubes to be provided with annular grooves for mounting sealing rings. The sealing rings can be mounted in these grooves to act as sealing elements and to provide an elastic seat for the distributor stub on the double tube. The sealing rings are mounted before the stub is pushed on, and compressed during the pushing-on process so as to form a tight seal, whereby expansion of the tubes and distributor stub owing to different temperature gradients can be compensated for. This, therefore, ensures a tight, elastic, and reliable seat for the distributor stub on the tubes. In particular, in an embodiment in which the outer tube is pushed over the outside of a cylindrical stub, only the sealing ring for the inner tube need be inserted within the bore. The second ring can be easily installed on the outside circumference of the stub in an annular groove provided therefor.
It is also possible to provide the connecting area for the outer tube in the bore next to the connecting area for the inner tube, whereby the outer tube then has an outer diameter corresponding to an inside diameter of the bore. In this case, the outer tube will also fit inside the bore of the stub. Inside, then, the bore will have these three areas of different diameters, whereby the chamber is formed in the middle area, the area of smallest diameter forms the connecting area for the inner tube, and the area of the largest diameter forms the connecting area for the outer tube. When the stub is pushed over the tubes, it strikes a stop, since it can only be pushed on until the outer tube strikes at the beginning of the middle bore, which has a smaller diameter than the outer diameter of the outer tube. Thus, the position of the stub is fixed in the axial direction toward the middle of the double tube.
In another advantageous embodiment of the invention, provision is made for the inner tube to have a length such that when the stub is mounted, it projects endwise beyond the stub in the axial direction. This end can then be bent, after applying the distributor stub, whereby a bilateral locking of the distributor stub on the double tube is accomplished along with the stop in the stub caused by the middle diameter of the bore. However, because the parts can be disassembled or replaced more easily, the inner tube is usually not crimped over the end of the stub.
Advantageously, provision is also made to equip the stub with a round, horizontal collar having an annular groove provided in the neck thereof, and to provide the neck of the stub with a thread. This enables a double-tube radiaton according to the invention to be fastened in simple fashion to a water radiator, for example, whereby a sealing ring mounted in the annular groove is pressed against the wall of the water tank by screwing down a screw mounted above the neck of the stub, thereby providing both a tight seal and a tight seat for the double-tube radiator. However, the double-tube radiator can also be mounted with spring elements (c.f. German Gebrauchsmuster No. 7713703).
To make it easier to slide the stub on the double tube, it is desirable to provide a transition from the bore in the middle area to the area of smallest diameter, as well as the ends of the bore, with bevels. These bevels make it easier to slide the parts together because these bevels guide the tubes into the bores when they are slid together. No such bevel is provided at the transition from the bore between the area of largest diameter and the area of medium diameter, since this transition serves as a stop for the outer tube.
A stub of this kind can be manufactured cheaply and economically as a casting. It can also be advantageous to make it in the form of an extruded section stamped or molded in a die, into which section the bore with the corresponding diameters can subsequently be formed.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.